Not possible to obtain Redrix Broadsword quest more than once
So the Redrix Broadsword quest has to be done individually on each character to obtain multiples.
However, I have 2 characters, and 1 of them completed the quest this season with the 5 valor resets.
The other character had not even bought the quest from Shaxx at that time.
However now, after completing the quest on character 1, I am no longer able to buy that quest from Shaxx this season anymore (however I could probably have done this quest more than once this season if I had bought it from Shaxx on character 2 BEFORE turning it in on character 1)
you won't be able to get the quest again since it is a season 4 quesf. now after you completed your quest on your first character, you will be able to get redrix broadsword from shaxx engrams (level up)